pixi global install exposes too much on existing environments

[Hofer-Julian]

Checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pixi, using pixi --version.

Reproducible example

$ pixi global install --expose ipython ipython
└── ipython: 8.29.0 (installed)
    └─ exposes: ipython

$ pixi global install --environment ipython ripgrep
└── ipython (installed)
    ├─ dependencies: ipython 8.29.0, ripgrep 14.1.1
    └─ exposes: ipython, ipython3, rg

Issue description

• Create a global environment where not everything is exposed
• Install into that environment with pixi global install
• Everything is now exposed

Expected behavior

In the example above, ipython3 should not have been exposed